Yamaha CV85 Alarm over 4000RPM

[MattMoore]

Hi, I have a Yamaha CV85 early 90's model that has an issue. When the motor has been over 4000RPM for over 3-4 minutes the alarm goes off and the motor shuts down. I will give it 5 minutes then the motor turns on and works fine unless I run it at over 4000RPM again for a similar period. I have no issues when I run below this RPM and there is always a solid stream running through the telltale.
Could someone please tell me why I am having this issue and how it can be fixed?

[boats.net]

Probably need to replace water pump.

[MattMoore]

Thanks. How difficult is that to replace or would i be better off taking it into the shop to get done?

[Bilge Rat]

Water pump replacement is not very difficult if you are mechanically inclined.

If the water pump has not been replaced in 2 years or more it needs to be done.
With cooling issues start at the source, the water pump.

If the motor is not overheating at low RPM you may also have an issue with the t-stat, poppet valve or scale buildup in the water jackets. Pull the T-stat and look at the insides of the water passages. If you see crud built up in there over 1/16" thick a good cleaning may be needed.

The age of the motor points to a complete inspection/cleaning of the cooling system. Water pump, t-stat, and poppet valve should be replaced every 2 years even if you have no problems, if not you will have problems soon.

[ausnoelm]

I would be thinking your water passages are near blocked, it is a very common symptom, you will probably need to remove the head and any cover plates you can find that will give you access to the water jackets, then you will have broken bolts to contend with as well.